Web Services A Standards-Based Framework for Integration

Web services are software components that can Web Services Web services standards are the glue that allows be accessed over the Web through standards- computers and devices to interact. UDDI based protocols such as HTTP or SMTP for use in allows clients to discover Web services. other applications. They provide a fundamentally new framework and set of standards for a UDDI Registry 1. Publish computing environment that can include servers, 2 1 2. Search workstations, desktop clients, and lightweight 3. Discover “pervasive” clients such as phones and PDAs. 3 4. Consume Web services are not limited to the ; they supply a powerful architecture for all types of . Web ArcWeb Web services standards are the glue that Applications Services allows computers and devices to interact, forming 4 a greater computing whole that can be accessed from any device on the network. UDDI allows clients to discover Web services. infrastructure through interoperability based on In Web services, computing nodes have three In a GIS context, the UDDI node plays the role of standardized interfaces. ESRI has built OGC- roles—client, service, and broker. a for registered Web services. A compliant connectors for ArcIMS that support n A client is any computer that accesses user can search the UDDI directory and locate the access to Web Map Services (WMS) and Web functions from one or more other computing distributed service providers or services that exist Feature Services (WFS). nodes on the network. Typical clients on a network. Web services can use a geographic framework include desktop computers, Web browsers, Web services interoperate (i.e., communicate) to fuse GIS applications. For example, a local Java applets, and mobile devices. A client through an XML-based protocol known as SOAP. government will be able to continuously maintain makes a request for a computing This is an XML API for the functions provided and update its land records while serving them to service and receives results for that request. by a . Each Web service advertises other organizations, both internal and external. n A service is a computing process that its SOAP API using WSDL that allows easy A utility company could directly use that local receives and responds to requests and discovery of any serviceʼs capabilities. governmentʼs basemap instead of maintaining its returns a set of results. Web services provide an open, interoperable, own and could serve its facilities data back to the n A broker is essentially a service metadata and highly efficient framework for implementing local government for use in permitting and land portal for registering and discovering systems. Software components communicate with use planning. This type of interorganizational services. Any network client can search the each other via standard SOAP and XML protocols. synergy will dynamically accelerate the use of portal for an appropriate service. A developer need only wrap an application with a geographic information everywhere. Because Web services can support the SOAP API and it can talk (either calling or serving) A spatial data infrastructure lets many integration of information and services that with other applications. Web services are efficient agencies and organizations share data stores and are maintained on a distributed network, they because they build on the stateless (i.e., loosely applications in a distributed environment. GIS are appealing to local governments and other coupled) environment of the Internet. A number fundamentally involves the integration of data from organizations that have departments that of nodes can be dynamically connected only when multiple sources. The Web services architecture independently collect and manage spatial data but needed to carry out a specific task such as updating establishes a specific type of relationship between must integrate these datasets. a or providing a particular service. service providers and information consumers The use of a connecting technology (Web Although the basic computer components of a that nicely supports the dynamic integration of services) coupled with an integrating technology Web services system are still clients and servers, data, which is the key to creating a spatial data (GIS) can efficiently support this requirement. network connections are dynamically created infrastructure. With the introduction of Web Various layers of information can be dynamically “just in time” and, therefore, do not require the services, distributed multivendor GIS services can queried and integrated but will still be maintained overhead of state-full (tightly coupled) networks. be dynamically integrated into applications using independently in a distributed computing These networks can be implemented in open as the interoperable standards of XML and SOAP. environment. ESRIʼs Web services technology, well as secure environments. Loosely coupled This level of integration is already available on the ArcWeb Services, is built on top of ArcIMS. architecture provides a new and promising desktop. ArcWeb Services leverage core business logic solution for implementing complex collaborative The ArcGIS Desktop products—ArcView, in ArcGIS and support Internet-based distributed applications such as a distributed GIS. ArcEditor, and ArcInfo—can fuse multiple computing. The integration of GIS and Web services ArcIMS services (e.g., map/image overlay). In A series of protocols—eXtensible Markup means that GIS can be more extensively the near future, ArcIMS will support integration Language (XML); Simple Object Access implemented. Mapping, data, and geoprocessing of these GIS services on a Web service tier. Protocol (SOAP); Web Service Description services are available from many servers and That means an applications developer can Language (WSDL); and Universal Description, can be integrated into a common environment. take several distributed GIS services, such as Discovery, and Integration (UDDI)—provides However, the ability to not only connect and mapping, geoprocessing, or data streaming, and the key standards for Web services and supports interoperate but also to integrate and fuse data build a new application anyone can use. This sophisticated communications between various based on geographic location, a capability Web tier environment, based on the XML/SOAP nodes on a network. These protocols enable that is inherent to GIS, makes GIS-based Web standards, will further enable ESRIʼs products to smarter communication and collaborative services unique. Web services can realize some dynamically integrate distributed GIS services processing among nodes built within any Web of the grand visions for GIS that include fusing from different GIS vendors that support Web services-compliant architecture. GIS applications and building a spatial data services standards. 40 ArcUser April–June 2003 www.esri.com